A lot of people have discovered the Discovery. Britain's favourite off-roader, more than any other vehicle, has beaten back its rivals from Japan and claimed victory with admirable British taste and understatement.

Chauvinist nonsense? Well, consider this. Not only is the Discovery the best-selling off-roader in Britain, it also outsells every 'executive' car - BMW 5-Series, Rover 800, Ford Granada, the lot. Even the Discovery's maker, Land Rover, admits to surprise at its popularity.

The success makes sense, though. A Discovery costs less than a Range Rover, yet is more modern and just as good. Indeed, beneath the body panels (aluminium in the Discovery's case, apart from the roof), the two cars are almost identical.

So we can be jolly proud of our all-British success story, notwithstanding that Land Rover is now owned by BMW. But wait a minute. Has the Discovery ever struck you as slightly, well, crude? Does the clatter of the turbodiesel engine found in most examples, the van- like front, the dated switchgear or the slow, heavy gearchange leave you with a niggling feeling that it was all done on the cheap?

If so, you are not alone. Faced with these shortcomings, Discovery-owners ready for a new car have found themselves tempted by the Japanese. The Mitsubishi Shogun, the Isuzu Trooper and the Nissan Terrano/Ford Maverick twins are butch and brash to look at, but their engineering is solid and sophisticated, and they feel more car- like to drive than the Discovery, with its vague steering.

Worse, Vauxhall is about to launch the Monterey, its own version of the Trooper, which will be in every town's Vauxhall dealer. So Land Rover, anxious to stay on top, has sent the Discovery to a health farm. It has come back refreshed and in fighting spirit.

See the new, single-slat grille, with its bigger, brighter headlamps. New bumpers, too, with 'crush cans' behind them to absorb impacts before the chassis is damaged. The flush windscreen is now glued in (as in most modern cars), the tail-lights are revised and the mirrors are bigger. Those are just the superficial signs of a new and very different Discovery. The suspension gains anti-roll bars to sharpen the handling. The turbodiesel engine has major revisions to virtually all its components except the cylinder block and crankshaft, and behind it lies a new gearbox with a shorter shift and a redesigned gate.

But the cabin is where the builders have really moved in. Out goes much of the Conran look, with its golf-ball dimples and defiant lack of leathergrain; in comes a new dashboard with updated switchgear, simpler and better-placed heater controls, and an altogether more solid feel - give or take the odd sticky switch action. The approach is less design-school, more establishment, to reflect the Discovery's new maturity. You can even buy a new ES version, with leather trim and lashings of luxury. Who needs a Range Rover now?

The former swimming-pool-blue colour has given way to 'granite grey', the better to stress solidity (the beige alternative remains available), and although the front passenger has lost the facia-mounted grab-handle, he or she now has the option of an airbag. The driver gets one as standard, mounted in a smaller steering wheel, remarkably like that of the Rover 800.

It is this smaller wheel that contributes much of the Discovery's new-found alertness. How so? Simply because for a given manoeuvre you do not have to move your hands as far. Combined with the new- found suspension tautness, which means that small steering movements now alter the Discovery's direction instead of merely tipping its body on its springs, the effect is startling. Today's Discovery responds more crisply than its rivals to the driver's demands. It feels much more like a normal car than before, yet retains the advantage of the high seating position so the driver can see over hedges and overtake on undulating roads.

None of this has compromised the Discovery's outstanding ability to plug its way through mud and mountains, while the permanent four-wheel drive (rivals have only rear-wheel drive for metalled roads) makes for secure roadholding.

The last thing you want in such a lofty vehicle is an untidy skid, and the Discovery will not let you down. You can now buy it with anti-lock brakes, too.

Then there is the revised turbodiesel engine. The output is unchanged, but the way the power is delivered is transformed.

Previously, an attempt to accelerate from low speed in second gear, as you might when emerging from a junction, was met with worrying inactivity from the engine until its turbocharger woke up. Now there is meaningful pull at low speeds, which transforms the Discovery's driveability. You can overtake with more confidence and change gear less frequently. When you do change gear, you will find a much lighter, slicker action to the shift. This, plus the engine's quieter running and the improved dynamic dexterity, all make today's Discovery a far nicer car to drive.

If you prefer, you can still specify a petrol-fuelled 3.9-litre V8 engine or a 2.0-litre four-cylinder; but, with its improvements, the diesel is the one to have.

The Discovery has come of age. I rue the disappearance of the alpine- scene graphic next to the name badge, itself now redesigned in crude capital letters; but Land Rover deems the graphic too frivolous for today's more mature Discovery. However, the marketing department is not wholly run by men of steel. The old turbodiesel engine was named 200 Tdi, after its approximate torque output. The new one, similarly muscular, is dubbed 300 Tdi. Why? Nobody at Land Rover seems to have the faintest idea.

Designed in Britain and made in Spain by Nissan (and also sold by that company as the Terrano), the Maverick is claimed to marry car-like driving qualities with decent off-road ability. It largely succeeds - and Ford dealers are the most plentiful of all.

Isuzu Trooper 3.1 TD Citation 5dr, pounds 24,399.

Still smoother and quieter than the Discovery, but bland inside and soggier in its handling. With cosmetic changes and a livelier interior, the Trooper is about to appear in your Vauxhall showroom as a Monterey (Isuzu is part-owned by General Motors).

Mitsubishi Shogun 2.8 TD 5dr, pounds 25,499.

One of the boldest and brashest of all, like a Trooper with more conviction and a more versatile four-wheel-drive system. Now with an enlarged and more responsive engine, the turbodiesel Shogun is a Discovery rival for the extrovert.

Toyota 4Runner 3.0 TD, pounds 23,211 Newly available in Britain, the 4Runner is based on the Hi-Lux pick-up beloved of builders. It doesn't show in the driving, which is more civilised than the muscle-bound looks suggest. The lift-down tailgate is a major irritation, because you have to retract the window every time you open it.